RFM Flags

V42 Flag: Simulate RFM v4.28

Flag will be discontinued from RFM v5 onwards
Run RFM v4.3 to replicate RFM v4.2 (specifically v4.28) results:
  1. Use polynomial expressions for Partition Sum calculations for Temperature dependence of HITRAN line strengths
  2. Extrapolate temperature dependence of cross-section data using (296/T)3/2 or molecule-specific rule

  1. Use 4th order Lagrangian interpolation for Partition Sums
  2. No temperature dependence of cross-section data beyond tabulated range.


  1. The new Lagrangian interpolation is more accurate since it interpolates data from tabulated values at 25K increments (module qtfct.for), whereas the old polynomial expression covered the range 70-500K with a single cubic fit (module qtfct_v42.for)
  2. The original RFM modifications for the temperature-dependence of tabulated cross-section data (module qtint.for) were inherited from GENLN2 (c1990s) and, while the 3/2 power rule might be reasonable for the central Q-branches it is the wrong sign for the wings. In any case cross-section data nowadays usually comes tabulated at a range of temperatures so extrapolation is generally not required.

[none reported]